Drill grinding apparatus



Feb. 16, 1965 L. s. KRULWICH DRILL. GRINDING APFARATUS 2 Sheets-Sheet 1 Filed Nov. 17, 1951 INVENTOR. in; 5. W

Feb. 16, 1965 I L. s. KRULWICH 3,169,353

DRILL GRINDING APPARATUS Filed Nov. 17, 1961 2 Sheets-Sheet 2 'f nsggulggggl INVENTOR.

United States Patent Ofifice 3,169,353 Patented Feb. id, 1965 3,169,353 DRILL GRENDENG AllARATUS Lester d. Kruiwich, 2:51 Central Park W New York 24-, N33. Filed Nov. 17, 1951, et. No. 153,020 4 tl'iaitns. (Cl. 51--2l9) This invention relates to improvements in apparatus for grinding drills, in particular to sharpen twist drills.

Most commonly twist drills are discarded when they become dull and some current manuals even recommend that this be done in view of what is now available to sharpen drills. The instruments are relatively like small complicated machines and certainly too expensive for occasional use, or else very informal and with little chance of sharpening the drill properly, ignoring key features of equal angle and length of the cutting lips, the clearance behind the cutting lips with the position of the heels and the small chisel edge on top.

An important object of this invention is to provide an apparatus for grinding drills that is easier to operate with a high degree of accuracy and is nevertheless less expensive to manufacture.

Another important object of this invention is to provide a drill grinding device which requires no further mechanical re-setting, clamping or regulating of any part after the drill has been placed in its holder.

Another object of this invention is to provide a drill grinding device in which the desired grinding angles are exactly pro-arranged.

Further objects and structural details of the invention will be apparent from the following description when read in conjunction with accompanying drawings forming a part of this specification, wherein:

FIG. 1 is a perspective view of an embodiment of my invention showing its use.

FIG. 2 is a section View taken along line 22 of FIG. 1.

FIG. 3 is a view similar to FlG. 2 with the addition of angle changing sections.

FIG. 4 is a top view of a conventional twist drill.

FIG. 5 is a side view thereof revealing the lip angles.

FIG. 6 is a sectional view taken along line 66 of FIG. 2.

FIG. 7 is a view similar to FIG. 6 showing a very small sized twist drill.

FIG. 8 is a view of an angle changing section shown in perspective.

FIG. 9 is a view similar to FIG. 8 providing for a different angle.

FIG. 10 is a View of my device shown in an alternate manner.

FIG. 11 is a view of the grinding wheel with an angled rim in accord with FIG. 10.

FIG. 12 is a view of another type grinding wheel with the outside part of the rim also angled.

FIG. 13 is a view of a grinding wheel with its rim provided with a plurality of suitable angles.

Upon reference to the drawings in detail, it will be noted that they show a drill grinding apparatus comprising a substantially triangular prism block 16 of wood or other suitable material with the angles at two of its triangular corners 11a, 1117 about equal to the angle generally used and conventionally made by each of the cutting lips 12 of twist drills 13 with its axis such as 59 degrees. The block 10 is wide enough to stand firmly on each of its lateral sides 14a, 14b, 14c for example one and a half inches wide with the edges of the triangular surfaces 15, 15a about four inches by four inches by four and a quarter inches. The two opposite lateral sides 14:2, 140 adjacent to the said two triangular corners 11a, 11b are optionally and preferably made with removable prism-shaped sec tions 16 as shown in FIGS. 3 and 8 having angles of about 112 degrees at the inner corners 17 formed with the third lateral side 14b so that their removal changes the angles at these two new corners 18 of the block it to about 68 degrees. Also a section 19 as shown in FIGS. 3 and 9 may similarly be added to each of these two lateral sides 14a, of the block 19 with the angles at these adjacent corners 2%} being about 121 degrees so as to bring the original angles from 59 degrees to the 49 degree angles 21. The removable sections have suitable fastening means such as threaded holes 22 extending through the lateral sides in said sections with retaining screws 23 long enough to hold all sections.

The lateral side 14b of the block 10 midway between the said two corners 11a, 11b contains an aperture 24 extending sidewise, its center line parallel to the lateral edges, with the opening on one side wider, such as threeeighths of an inch and converging to a point as shown in FIGS. 6, 7 and 10; the aperture 24 extends longitudinally downwards at right angles to the lateral surface with a closed bottom 26, adapted to accommodate intimately at least the shank 27 of ditferent sizes of twist drills. Through the triangular face 15 of the block 10, about an inch below the top of the aperture 24, a thumb screw 28, or other appropriate means, enters a threaded hole 29 right angularly into the center of the larger side of the aperture 24- with space 30 cleared away in the opposite corner wall 25 of the aperture 2% so that the end of the thumb screw 28 can continue fully into the far corner thus enabling the thumb screw 28 to engage and firmly hold in position very small twist drills ida, FIG. 7, as well as popular sized 13 twist drills.

A short space from the edges on each of the two lateral sides 14 a, 14c opposite the aperture 24 three holes 3 1 are drilled in a line parallel to the said edges, extending up wards perpendicularly to the lateral surface so as to receive, with freedom allowed for pivoting, a post or headless nail 32 protruding from a sheet of wood or work table 33, adapted so that when the block W rests on either of these lateral sides 14a, 140, the block It? may be swung from side to side, pivoting on the post or nail 32-.

Optionally, on the other triangular side 15a, approximately opposite the thumb screw 28, a relatively small oblong 34, of wood or otherwise, is centrally attached by cementing or any appropriate means, longitudinally at right angles to the lateral surface 141) containing the aperture 24 and with the two bottom sides 35 of the oblong curved so that it may be oscillated from side to side when the block Iltl rests on that triangular side 15a.

Optionally and preferably at both sides of the aperture 24 on the block 15?, marks 36 or other indicia are afiixed by any suitable means showing the position of the controlling parts, as illustrated in FIG. 4, of the twist drill such as the cutting lips 12a, heels 37 and chisel edge 38 as they properly appear from above facing each of these sides.

While an ordinary grinding wheel 3% may be used, optionally in conjunction with the device there is provided a grinding wheel 48 in FIGS. 10, 11 having its lateral curved rim 41 bevelled inward to form a recessed angle 42 about equal to the point angle 12 of the drill 13 being ground such as the angle of 118 degrees, so that the lips of the twist drill 13 and the surface behind it will fit into the angle 42 in the rim 41 of the wheel 40 engaging its sides. The angle in the wheel may be formed integrally or may be provided by joining two separate wheels, the inner side of each being bevelled, for instance to a 59 degree angle and together forming the 118 degrees. Wheels with rims angled inward to about 136 degrees and 98 degrees are also to be employed; and two bevelled wheels 43 in FIG. 12 being joined to form an angle may also have bevelled angles 44 on the outer sides of the lateral rim so as to supply an additional re- -45 in F1813, integrally or otherwise, may contain on its curved lateral rim aplurality of different recessed angles 46a, 46b, the running in a curved line parallel to each other. The angles used here approximate the point angles generally employed for medium, hard and soft metals but any angles suitable for the points of the drills may be used.

PEG. 1 and the other drawings show the fundamental operation of the device.

lock fill with these two corner angle lla, 11b is ern-. ployed. The aperture 24 is large. enough to receive a drill of any size up to three-eighths of an inch but can be made to accommodate larger sizes. The shank 27 is inserted in the aperture 24 with the body of the drill 13 mostly extending'outside. With unusually small sizes,

the drill may be set farther out to be withineasie-r reach.

of the grinding wheel 39; The block 1% rests on either of the lateral'sides 14a, 14c adjacent to the one 14!) containing the aperture 24. The corner angle lla determines the angular inclination of the drill l3 projecting towards the Vertical face of the grinding wheel 3%. As the drill 13 extending out of the aperture 2 is per pendicular to that lateral surface 14b, the angle at the top 'of the drill is formed by the axis of the drill 13 and a line extending vertically down becomes the same as the bottom corner angle, in this instance 59 degrees,

I which 'is substantially the angle to which each cutting lip is being ground.

The top of the drill FlGS. 4, is set with each of the surfaces in back of the cutting lips approximately facing one of the lateral edges of that side 14b and with the full lip angle of 118 degrees, in this instance, clearly dis cernible at eye-level above the thumb screw 23 or from the opposite side To insure an accurate setting the marks 36 on each side of the aperture 24 or elsewhere are followed indicating the correct relative position of the cutting lips 12a, heels 3.7, chisel edge 38 and other controlling points. The thumb screw 23 is tightened with its end engaging the shank 27 of the drill 13 and pressing it against the inside walls 25 of the aperture 24 so that the drill 13 extends out perpendicularly to the surface of that lateral side 14b. The partial extension 36 of the screw hole 29 through the opposite corner of the aperture wall 25 permits the screw end to hold. securely against the smallest twist drill 13m, FIG. 7 set .in the far corner. i

The block ill is placed on the pivoting post 32 through the one of the three holes 31 nearest in line with the projecting drill 13. The flat face or" a grinding wheel 39 is used, preferably of medium grain and soft grade, on

The angle of each cutting lip' on most twist drills is about 59 degrees and for these the with a light grind which is usually preferable.

of the drill in the recessed angle 42.. Any inequality in the length of the cutting lips or their angles becomes apparent and is readily corrected by grinding the particular side without re-setting the drill and without any mechanical adjustment. The angled rimll of this wheel lll may also be used to remove the burr behind the cutting lips.

The grinding wheel FIGS. 10, ll, 12, 13 with the angled lateral rim may be employed to adjust the grinding of the drill, but it may optionally also be initially used to grind and sharpen the lips of the drill, especially The position of the drill l3 the aperture remains the same. The block 16 is placed on its triangular side 1502 resting on the oblong 34'. The pivot holes 31 and post 32 are not used. The drill 13 projects outwardly horizontally in line with the center of the curved angle 42 of the wheel rim The fiat face of the wheel stays in a vertical position with the drill head entering the wheel rim angle 42 and engaging it for light grinding. If the wheel PEG. 13 is recessed with a plurality of angles 46a, 46b, sec, naturally the one that is about the same as the point angle 12 is used. The block id is oscillated from side to side a few times on the oblong 34 thereby effecting the. complete grinding of the surface behind the cutting lips; the extent or limit of the oscillation being controlled by the width of the oblong 34-. With this optional and supplemental apparatus the fiat face of the wheel may then be employed'for any necessary adjustments in the grinding by simply changing back the positionof the block ill still without doing any clamping or unclamping whatsoever.

What I claim is:

1. An apparatus for gindhig the cutting lips of a drill, comprising a block substantially in the form of a trian gular prism having three latenal faces intersecting at predetermined angles to form three corners which respectively terminate in three lateral edges, the angles between said lateral faces at the corners which terminate in two of said lateral edges being about the same as an angle of each of the cutting lips of the drill being ground, having a plurality of removable sections at said corners with fastening means adapted to'increase or decrease the said corner angles so that they coincide with other angles of such cutting lips, an aperture midway on the lateral face between the said two corners extending longitudinally downwards into the said block at right angles to the surface of the said lateral face designed to accommodate 7 the lower portion of drills of various sizes whereby the either a stationary motor or an electric hand drill The face of the wheel 39 remains vertical and is first set at right angles to the triangular surfaces of the block it The wheel and drill head are brought close enough together for only relatively light grinding strokes. The hand grips the back or top of the block 16 and swivels it from side to side sufficiently to clear the grinding wheel 39. This is begun somewhat ofi the right angular line between the wheel face and the block .16 to accomplish the grinding but the pivot swing is made equally on both sides. After grinding one side of the drill 13, the block 10 is turned over to rest on the opposite lateral side Me with the corner llb having the same angle to the front and the opposite hole 31 being used on the pivot post 32. The same method of grinding is The grinding wheel upper portion of the dhfll extends out perpendicularly to the surface of the said lateral face, adapted so that when the block rests on either of its two other lateral faces, the angles at the said corners determine the angular inclination of the drill projecting towards a' vertical grinding wheel which thereby imparts the same angle to a cutting lip of the drill, a screw extending through a wall of the aperture with space provided in the opposite part of the aperture whereby the end of the screw can continue fully to engag'e drills of various sizes, the two lateral faces opposite the aperture having holes for accommodation of a post whereby the block may be oscillated.

' 2. An apparatus for grinding the cutting lips of a drill, comprising a block substantially in the form of a triangular prism having three latenall faces intersecting at predetermined anglesto form three corners which respectively terminate in three lateral edges, the angles between said'lateral faces at the corners which terminate in two of said lateral edges being about the same as an angle of each of thecutting lips of the drill being ground, with means to increase or decrease the said corner angles so that they coincide with other angles of such cutting lips, an aperture midway on the lateral face between the said two corners extending longitudinally downwards into the said block at right angles to the surface of the lateral face designed to accommodate the lower portion of drills of various sizes whereby the upper portion of the drill extends out perpendicularly to the surface of the said lateral face, adapted so that when the block rests on either of its two other lateral faces, the angles at the said corners determine the angular inclination of the drill projecting towards a vertical grinding wheel which thereby imparts the same angle to a cutting lip of the drill, a screw extending through a wall of the aperture with space provided in the opposite part of the aperture whereby the end of the screw can continue fully to engage drills of various sizes, the two lateral faces opposite the aperture having holes for accommodation of a post whereby the block may be oscillated.

3. An apparatus for grinding the cutting lips of a drill, comprising a block substantially in the form of a triangular prism having three lateral faces intersecting at predetermined angles to form three corners which respectively terminate in three lateral edges, the angles between said lateral faces at the corners which terminate in two of said lateral edges being about the same as an angle of each of the cutting lips of the drill being ground, an aperture midway on the lateral face between the said two corners extending longitudinally downwards into the said block at right angles to the surface of the said lateral face desi ned to accommodate the lower portion of drills of various sizes whereby the upper portion of the drill extends out perpendicularly to the surface of the said lateral face, adapted so that when the block rests on either of its two other lateral faces, the angles at the said corners determine the angular inclination of the drill projecting towards a vertical grinding wheel which thereby imparts the same angle to a cutting lip of the drill, a screw extending through a wall of the aperture with space provided in the opposite part of the aperture whereby the end of the screw can continue fully to engage drills of various sizes, the two lateral faces opposite the aperture having holes for accommodation of a post whereby the block may be oscillated.

4. An apparatus for grinding the cutting lips of a drill, comprising a block substantially in the form of a triangular prism having three lateral faces intersecting at predetermined angles to form three corners which respectively terminate in three lateral edges, the angles between said lateral faces at the corners which terminate in two of said lateral edges being about the same as an angle of each of the cutting lips of the drill being ground, an aperture midway on the lateral face between the said two corners extending longitudinally downwards into the said block at right angles to the surface of the said lateral face designed to accommodate the lower portion of drills of various sizes, with means holding the drill in the aperture with its upper portion extending out perpendicularly to the surface of the said lateral face, adapted so that when the block rests on either of its two other lateral faces, the angles at the said corners determine the angular inclination of the drill projecting towards a vertical grinding wheel which thereby imparts the same angle to a cutting lip of the drill, the two lateral faces opposite the aperture having holes for accommodation of a post whereby the block may be oscillated.

References tilted in the file of this patent UNITED STATES PATENTS 288,069 Landers Nov. 6, 1883 643,927 Walker Feb. 20, 1900 1,184,340 Gettings May 23, 1916 1,308,430 Lentatz July 1, 1919 1,908,155 Jorgensen May 9, 1933 

4. AN APPARATUS FOR GRINDING THE CUTTING LIPS OF A DRILL, COMPRISING A BLOCK SUBSTANTIALLY IN THE FORM OF A TRIANGULAR PRISM HAVING THREE LATERAL FACES INTERSECTING AT PREDETERMINED ANGLES TO FORM THREE CORNERS WHICH RESPECTIVELY TERMINATE IN THREE LATERAL EDGES, THE ANGLES BETWEEN SAID LATERAL FACES AT THE CORNERS WHICH TERMINATE IN TWO OF SAID LATERAL EDGES BEING ABOUT THE SAME AS AN ANGLE OF EACH OF THE CUTTING LIPS OF THE DRILL BEING GROUND, AN APERTURE MIDWAY ON THE LATERAL FACE BETWEEN THE SAID TWO CORNERS EXTENDING LONGITUDINALLY DOWNWARDS INTO THE SAID BLOCK AT RIGHT ANGLES TO THE SURFACE OF THE SAID LATERAL FACE DESIGNED TO ACCOMMODATE THE LOWER PORTION OF DRILLS OF VARIOUS SIZES, WITH MEANS HOLDING THE DRILL IN THE APERTURE WITH ITS UPPER PORTION EXTENDING OUT PERPENDICULARLY TO THE SURFACE OF THE SAID LATERAL FACE, ADAPTD SO THAT WHEN THE BLOCK RESTS ON EITHER OF ITS TWO OTHER LATERAL FACES, THE ANGLES AT THE SAID CORNERS DETERMINE THE ANGULAR INCLINATION OF THE DRILL PROJECTING TOWARDS A VERTICAL GRINDING WHEEL WHICH THEREBY IMPARTS THE SAME ANGLE TO A CUTTING LIP OF THE DRILL, THE TWO LATERAL FACES OPPOSITE THE APERTURE HAVING HOLES FOR ACCOMMODATION OF A POST WHEREBY THE BLOCK MAY BE OSCILLATED. 